1. Field
The present disclosure relates to a control system design assist device, a control system design assist program, a control system design assist method, an operation change amount calculation device and a control device.
2. Description of Related Art
PID (Proportional-Integral-Derivative) control has been used widely in the prior art as a control method in a control system. This PID control system yields particularly good control performance in respect of control objects (plants) where the transfer function is expressed by integral elements, first-order delay elements, waste time elements, second-order delay elements, or the like. Furthermore, various methods for adjusting the PID parameters are known, such as a limit sensitivity method, CHR (Chien-Hrones-Reswick) method, or the like. However, in PID control, the operation amount varies to a greater extent, the larger the difference between the target value and the control amount, and therefore if an inverse response occurs in which the control amount changes in the opposite direction to the target value, with change in the operation amount, then undershooting may occur, and the control system may become instable.
Consequently, Non-Patent Document 1, for example, discloses a PID parameter adjustment method which is compatible with inverse response characteristics, by approximating a loop transfer function with an integral element (K/s), when the transfer function of the control object is expressed by a combination of waste time elements and first-order advance and delay elements. Furthermore, Non-Patent Document 2 or Non-Patent Document 3, for example, disclose model prediction control in which optimization control is carried out by using a state space model and/or time response model of the control object, instead of PID control. Moreover, Non-Patent Document 4, for example, in addition to disclosing standard model prediction control involving on-line execution of a numerical optimization algorithm, also discloses model prediction control in which on-line numerical optimization is made unnecessary by carrying out off-line calculation in advance.
On the other hand, individual inverse response countermeasures are also carried out in respect of particular control objects. For example, Patent Document 1 discloses a boiler drum level control device which carries out feed-forward compensation in order to cancel out inverse response in boiler level control. Furthermore, Patent Document 2, for example, discloses a load control method for a waste-burning power generation plant, in which a combustion air volume is adjusted prior to load variation, and furthermore, inverse response in the event of an increase in the load is suppressed by adjusting the amount of introduced waste after a delay with respect to load variation.
Moreover, technology is also known in which a system control problem, or the like, is expressed as a first-order predicate logical formula, and system optimization is carried out by solving this formula (see, for example, Non-Patent Document 5). More specifically, a first-order predicate logical formula is obtained in which universal quantifiers (∀) or existential quantifiers (∃), which are known generally as quantifiers, are applied to a portion of the variables in a logical formula in which polynomial equations and/or inequalities are joined by connectives, such as logical product (∧) or logical sum (∨), and the like. System optimization is then carried out by eliminating the variables (bound variables) to which a quantifier has been attached in the first-order predicate logical formula, and deriving a logical formula in which the other variables (free variables) are to be satisfied. For example, Patent Document 3 discloses a control system analysis and design device which converts a control system to a first-order predicate logical formula and analyzes the control system on the basis of this first-order predicate logical formula after eliminating the variables to which a quantifier is attached.